Parallel-pole circuit breaker

ABSTRACT

A FOUR-POLE CIRCUIT BREAKER HAVING TWO LINE TERMINALS AND TWO LOAD TERMINALS, EACH TERMINAL SERVING TWO POLES ELECTRICALLY CONNECTED IN PARALLEL. THE MOVABLE CONTACT ARMS OF EACH PAIR OF PARALLEL POLES ARE CONNECTED TO A SINGLE THERMAL AND MAGNETIC TRIPPING DEVICE IN ONE POLE SPACE, THE OTHER POLE SPACE HAVING NO TRIPPING DEVICE BUT BEING PROVIDED WITH A LATCH WHICH ALSO SERVES AS A TRIP   INDICATOR FOR THE CIRCUIT BREAKER WHEN THE POLE SPACE IS PROVIDED WITH A WINDOW.

F. E.CHABOT PARALLEL-POLE CIRCUIT BREAKER Dec. 12,- 1972 Filed Aug. 9, 1971 3 Sheets-Sheet 1 INVENTOR. FERDI N AND E. CHABOT Egg az LJ M Q FIG. 3

Dec. 12, 1972 F. E; CHABO-r 3,706,056

PARALLEL-POLE cmcum BREAKER Filed Aug. 9, 1971 3 Sheets-Sheet 26 I l l INVENTOR. FERDINAND E. CHABOT Dec. 12, 1972 F. E. CHABOT 3,706,056

IPARALLEL-POLE CIRCUIT BREAKER Filed Aug. 9, 1971 3 Sheets-Sheet 5 INVENTOR. FERDINAND E. CHABOT United States Patent 3,706,056 PARALLEL-POLE CIRCUIT BREAKER Ferdinand E. Chabot, Cedar Rapids, Iowa, assignor to Square D Company, Park Ridge, 1]]. Filed Aug. 9, 1971, Ser. No. 170,106 Int. Cl. H01h 73/48 US. Cl. 335-- 2 Claims ABSTRACT OF THE DISCLOSURE The present invention is a modification of the circuit breakers disclosed in US. Pats. 3,061,697, issued Oct. 30, 1962, and 3,159,048, issued Dec. 1, 1964. The former patent discloses a single-pole circuit breaker, while the latter patent discloses a handle tie means used when two two-pole circuit breakers similar to that of the former patent are secured together side-by-side to form a fourpole circuit breaker.

Existing panelboards accept circuit breakers of a certain maximum normal current carrying capacity. It has become desirable to increase the normal current carrying capacity of these circuit breakers because of larger electic loads such as are encountered in electric heating. One way by which this has been accomplished in the past is by mounting two single-pole circuit breakers side-by-side and electrically connecting them in parallel, but providing only one plug-on line terminal feeding two stationary contacts and only one load terminal connected to two movable contact arms through two thermally and magnetically operable tripping devices. With such a construction, one-half the total load through the single line and load terminals flows through each of the two-poles, and the total load can be larger than the maximum normal current carrying capacity of each pole.

In accordance with the present invention, two single pole circuit breakers provided with only one line and one load terminal are electrically connected in parallel, the movable contact arms of the two poles being electrically connected to only one thermal and magnetic tripping device located in one of the pole spaces. The elimination of the tripping device in the other pole space reduces the cost of the circuit breaker, reduces the amount of heat generated in the circuit breaker and panelboard, and makes space available for a trip indicating means.

An object of the invention is to provide an improved circuit breaker of the parallel-pole type for plugging into an existing panelboard to service larger electrical loads than the maximum normal current carrying capacity of the highest rated single-pole circuit breaker for the panelboard.

Another object is to provide a circuit breaker of the parallel-pole type which is less expensive to manufacture and generates less heat than former similarly rated parallel-pole circuit breakers.

A further object is to provide a circuit breaker of the parallel-pole type with a latch member in one pole, the latch member also serving as a trip indicating device visible through a window in the casing of the circuit breaker.

Other objects and advantages will appear when the following specification is considered along with the accompanying drawings in which:

FIG. 1 is a front view, partially in section, of a circuit breaker constructed in accordance with the invention and having two pairs of double poles electrically connected in parallel;

FIG. 2 is a sectional view taken generally along the line 2-2 of FIG. 1 and showing a first pole of the circuit breaker;

FIG. 3 is an end view of the circuit breaker taken in the direction of arrows 3-3 in FIG. 1;

FIG. 4 is a sectional view taken generally along the line 44 of FIG. 1 and showing a second pole of the circuit breaker;

FIG. 5 is an enlarged fragmentary sectional view of the circuit breaker of FIG. 1 taken along the line 55 of FIG. 2;

FIG. 6 is a plan view of a plug-on line terminal jaw member, terminal strap, and stationary contact assembly serving the first and second poles of the circuit breaker;

'FIG. 7 is a side view of the assembly of FIG. 6;

FIG. 8 is a plan view of a movable contact arm of one of the poles of the circuit breaker;

FIG. 9 is a side view of a contact arm and tripping device assembly showing the movable contact arms of two poles connected to a single tripping device of one pole of the circuit breaker;

FIG. 10 is a plan view of a plug-on line terminal jaw member, terminal strap, and stationary contact assembly serving the third and fourth poles of the circuit breaker; and

FIG. 11 is a side view of the assembly of FIG. 10.

With reference to the drawings, FIGS. 1 and 3 show a four-pole circuit breaker 12 constructed in accordance with the invention and comprising two two-pole circuit breakers 13 and 14 secured together by three rivets 16 (FIGS. 1, 2, and 4). Each of the circuit breakers 13 and 14 has a three-part molded case including a base member 18, a combined base and cover member 19, and a cover member 20 secured together by three rivets 22. The members 18 and 19 provide a compartment in which parts of one pole are mounted, and the members 19 and 20 provide another compartment in which parts of another pole are mounted.

For ease of description, reference is made to first, second, third, and fourth poles of the circuit breaker 12, the parts of the first pole being mounted generally in a base portion of the member 19 of the circuit breaker 13, as best shown in FIG. 2, and the parts of the second pole being mounted generally in the base member 18 of the circuit breaker 13, as best shown in FIG. 4. Parts of the 1 third and fourth poles are respectively mounted generally in the corresponding members 19 and 18 of the circuit breaker 14.

The first and second poles are electrically connected in parallel. To this end, the second pole is provided with a plug-on line terminal jaw member 24 as best shown in FIGS. 4, 6, and 7. The jaw member 24 is secured to a generally L-shaped terminal strap 25 having a pair of stationary contacts 26 and 27 secured thereto. The contact 26 is disposed in the second pole, andthe contact 27 is disposed in the first pole.

The first pole (FIG. 2) is provided with a terminal strap 28 secured in place by a screw 30 threaded into a trapped nut 31; An angularly disposed outer end portion 28a- (FIG. 3) of the terminal strap 28 is provided with a connector body 32 having a clamping screw 34 threadedly mounted therein for clamping of a load wire (not shown).

A thermally and magnetically operable tripping device 36 is secured to an inner end portion of the terminal strap 28. The tripping device 36 is fully described in the aforementioned Pat. 3,061,697, is shown out of the case in FIG. 9, and includes a bimetallic strip 38 secured to the terminal strap 28, a magnetic yoke or core 39 secured to the bimetallic strip 38, a bimetallic armature 40 pivotally mounted in upper side arm portions of the core 39 and retained adjacent its lower end in an apertured tail portion of the core 39, a compression spring 41 biasing the lower end portion of the armature 40 away from the core 39, and an ambient temperature compensating bimetallic strip 42 secured to an upper end portion of the armature 40.

In accordance with the invention, a pair of movable contact arms 44 and 45 are electrically connected to the bimetallic strip 38, as best shown in FIG. 9, respectively by a pair of flexible braided wire conductors 46 and 47 each having an end portion welded between the core 39 and the bimetallic strip 38. The contact arms 44 and 45 are provided respectively with a pair contacts 48 and 49 engageable respectively with the stationary contacts 27 and 26. Each contact arm is also provided with an arc shield 50 formed of insulating material and retained in place by a pin 51 (-FIG. 8) inserted through a tang 50a extending through a portion of the contact arm.

The contact arm 44 is disposed in the first pole (FIG. 2), and the contact arm 45 is disposed in the second pole (FIG. 4). The conductor 47 is longer than the conductor 46, since it must extend from the contact arm 45 in the second pole through the respective case member 19 to the bimetallic strip 38 in the first pole.

The current path through the circuit breaker 13 is from the terminal jaw member 24 through the terminal strap 25 and then in parallel paths through the stationary contacts 27 and 26, through the movable contacts 48 and 49, through the contact arms 44 and 45, through the flexible conductors 46 and 47, and then in a single path through the bimetallic strip 38, and through the terminal strap 28 to the connector body 32.

The remaining parts in the first pole are conventional. The bimetallic strip 42 acts as a latch for a trip lever 52 pivotally mounted on a boss 19a of the casing and carrying a reset pin 53. A tension spring 54 is connected at one end to the trip lever 52 and at the other end to a bight portion of a generally U-shaped link 56, the bight portion extending through slots in opposite side wall portions of the contact arm 44, which is pivotally mounted on a pin 57. The link 56 is pivotally connected to a link 58 which is also mounted on the pin 57 and carries a drive pin 59 operable by a pivotable dummy handle 60 keyed to a handle 61 in the second pole by a rectangular shaft 62. The handle arrangement is more fully disclosed in the aforementioned Pat. 3,159,048 and includes a handle tie member 63 tying the handle 61 in the second pole to a handle 64 in the third pole. A retractible handle lock member 65, as disclosed in US. Pat. 3,426,164, issued Feb. 4, 1969, is provided between the second and third poles and is shown in extended position in FIG. 4.

Common trip means are provided for the four poles of the circuit breaker 12. Thus, a rectangular shaft 66 extends across the four poles as best shown in FIG. 5. Four cam members 67 are keyed to the shaft 66, one being disposed in each pole. The trip lever 52 in each pole has an offset tang 52a (FIG. 2) which engages the respective cam 67 upon tripping of the circuit breaker and rotates the shaft 66, thereby rotating the cams 67 in the other poles and moving their-respective latch members to release their trip levers.

Only the first and third poles are provided with tripping devices 36 as shown in FIG. 2 for the first pole. In each of the second and fourth poles, the tripping device 36, terminal strap 28, screw 30, and nut 31 are replaced by a pivotally mounted latch member 68 biased clockwise as viewed in FIG; 4 toward latching position with respect to the respective trip lever 52 by a compression spring 69.

The second pole is provided with a'window =70 (FIGS. 1 and 4), and the latch member 68 therein is provided with an indicating end portion 68a which may be brightly painted to indicate a tripped condition of the circuit breaker when it is moved into alignment with the window by its respective cam 67.

The third pole is provided with a plug-on line terminal jaw member 72 identical to the jaw member 24 and shown in FIGS. 10 and 11. The jaw member 72 is secured to a generally L-shaped terminal strap 73 having a pair of stationary contacts 74 and 75 secured thereto. The contact 74 is disposed in the third pole, and the contact 75 is disposed in the fourth pole. An arc runner 77 also is secured to the terminal strap 73 adjacent the contact 75.

The third pole is substantially identical to the first pole of FIG. 2, exceptions being that the third pole has the full handle 64 in place of the dummy handle 60, and that the third pole has the jaw member 72 while the first pole is fed from the jaw member 24 of the second pole. Thus, the third pole has a tripping device like the device 36, and contact arms like the arms 44 and 45 of the first and second poles are disposed respectively in the third and fourth poles and electrically connected to the tripping device in the third pole.

The fourth pole is substantially identical to the second pole of FIG. 4, exceptions being that the fourth pole has a dummy handle similar to the dummy handle 60 of the first pole in place of the full handle 61, that the fourth pole is fed from the jaw member 72 of the third pole while the second pole has the jaw member 24, and that the fourth pole has no window 70. Thus, the fourth pole has a latch member like the latch member 68.

Each pole is provided with a conventional arc chute 79 (FIGS. 2 and 4) including a plurality of spaced, generally U-shaped metal plates 80. The first, second, and third poles are each provided with an arc runner 81 similar to the arc runner 77 in the fourth pole, except that the arc runners 81 are loosely assembled in place. For assembly purposes, the arc runner 77 is welded to the terminal strap 73. The first and fourth poles are each provided with a pair of mounting clips 82 for mechanically connecting the circuit breaker 12 to the mounting pan of an electrical panelboard. The first and third poles are each provided with a calibrating screw 84 (FIG. 2) threadedly mounted in a trapped nut 85 and engageable with the inner end portion of the terminal strap 28 to adjust the tripping point of the tripping device 36 by bending the terminal strap and thereby changing the amount of overlap between the bimetallic latching strip 42and the trip lever 52 in the latched position.

Various modifications may be made in the structure shown and described without departing from the'spirit and scope of the invention.

I claim:

1. A parallel-pole electric circuit breaker comprising" a casing defining a pair of side-by-side compartments; pair of stationary contacts disposed respectively in the compartments, a line terminal accessible from the outside of the casing and electrically connected to both of the stationary contacts, a pair of movable contact arms pivotally mounted'respectively in the compartments,- a pair of movable contacts mounted respectively on the contact arms and movable thereby into and out of engagement respectively with the stationary contacts, a pair of releasably latchable trip levers pivotally mounted respectively in the compartments and respectively releasable from a latched position to effect movement of the contact arms thereby to effect disengagement of the movable contacts respectively from the stationary contacts, a thermally and magnetically operable tripping device disposed in one of the compartments and releasably latching the trip lever therein, a latch member in the other of the compartments releasably latching the trip lever therein, a conductor in the one compartment having one end portion electrically connected to the movable contact arm therein and an opposite end portion electrically connected to the tripping device, a conductor having one end portion in the other compartment electrically connected to the movable contact arm therein and an opposite end portion in the one compartment electrically connected to the tripping device, means for moving the latch member to release the trip lever in the other compartment upon operation of the tripping device and release of the trip lever in the one compartment, and a load terminal accessible from the outside of the casing and electrically connected to the tripping device.

2. A circuit breaker as claimed in claim 1 including a window in a portion of the casing defining the other compartment and wherein the latch member is provided with an indicating end portion which is moved into alignment with the window to indicate a tripped condition of the circuit breaker upon tripping thereof by the tripping device.

References Cited UNITED STATES PATENTS 3,152,287 10/1964 Edmunds 31746 3,401,363 9/1968 Yyskocil et a1 335-10 10 HAROLD BROOME, Primary Examiner US. Cl. X.R. 335-23 

